Effect of organised screening on cervical cancer incidence and mortality in Finland, 1963-1995: recent increase in cervical cancer incidence.

A nation-wide screening programme for cervical cancer started in Finland gradually from 1963 onwards. By the beginning of the 1990s, there had been a decrease of 80% both in the age-adjusted incidence of and mortality from cervical cancer. To describe the recent patterns in cervical cancer incidence and mortality and evaluate their differentials in relation with the organised screening activities, we have updated the material on the cervical cancer incidence and mortality as well as mass-screening activities up to the year 1995. Based on the files of the Finnish Cancer Registry, there is a striking increase of about 60% in the incidence of cervical cancer during the last 4 years of the study period among women below 55 years of age. The mortality rates are still decreasing. There is no overall decrease over recent years in the coverage of the programme invitations or smears taken. Incidence of invasive cancer and of moderate and severe dysplasia as detected in mass screening have increased. As to the interpretation, changes in the risk factors, such as in sexual behaviour and smoking habits, over the decades might partly explain increasing trends in cervical cancer incidence. As the change in incidence was relatively abrupt, inadequacies or changes in the effectiveness in the screening programme, particularly among young women, may also have contributed. Expanding the coverage of and attendance in the pap-screening programme among women in young target ages would still be effective. Increasing emphasis on quality assessment in screening is also needed.

Cancer patient survival--patterns, comparisons, trends--a population-based Cancer Registry study in Finland.

The effects of primary site, sex, age, stage and histological type on cancer patient survival were analysed on the basis of the population-based material of the Finnish Cancer Registry from 1985 to 1994. In addition, trends in survival were constructed for the period 1955-1994. Detailed site-specific data are published as Supplement 12 to Vol. 38 of Acta Oncologica. Within a given site, the survival differences by gender were not large. However, because of different site distributions, the average prognosis for female patients, all sites taken together, was superior to that of males: the 5-year relative survival rates (RSR) were 58% and 43%, respectively. In general, older patients had a poorer outcome compared with younger patients (partly because of different stage and histology distributions). Stage was a strong determinant of patient survival. In some cancers with a poor average prognosis the 5-year RSR for localized tumours was reasonable, e.g. 61% for stomach cancer, males, 34% for gallbladder cancer, females, and 29% for lung cancer, males. Most of the survival rates clearly increased over time. In addition to improvements in cancer treatment, changes over time in several other factors affect the trends, such as changes in the stage distribution (early diagnosis as a result of health education, improved diagnostic methods, screening, etc.) and in the composition of the patient material because of changing definitions of cancer (e.g. papilloma versus papillary carcinoma of the bladder, occult carcinoma of the thyroid, and early prostate cancer). The large Cancer Registry material (466,000 patients) enabled accurate estimates of the survival rates of cancer patients in Finland. These rates reflect the effectiveness of the healthcare system as a whole and are useful for planning and evaluation purposes. However, the estimated survival rates are based on grouped data, and cannot be directly applied for predicting the prognoses of individual patients, although they can be used as guidelines.

Survival of cancer patients in Finland 1955-1994.

INTRODUCTION: The study of survival of cancer patients is essential for monitoring the effectiveness of cancer control. The previous monograph describing cancer patient survival in Finland was published by the Finnish Cancer Registry in 1981 and covered patients diagnosed in 1953-1974. This new supplement assesses cancer patient survival up to the year 1995. MATERIAL AND METHODS: The study includes over 560000 tumours registered at the Finnish Cancer Registry with a date of diagnosis between 1955 and 1994. Patients were followed up to the end of 1995. Trends in relative survival rates are studied over four 10-year diagnostic periods from 1955 to 1994. In addition, detailed results are presented for patients diagnosed during 1985-1994, including relative survival rates tabulated by stage, sex, and age. Additional sections describe differences in cancer patient survival according to social class and region of residence and a comparison of cancer patient survival in Finland to other European countries. RESULTS: Patient survival improved over time for almost all anatomical sites. The main exception is in cancer of the cervix uteri, where patient survival has decreased slightly from 1965-1974 to 1985-1994 due to the selective prevention of less aggressive tumours through cytologic screening. Very few differences in patient survival are observed between males and females. A substantial improvement in survival can be seen for childhood cancers. CONCLUSION: The increasing survival rates reflect improvements that have taken place in various areas of cancer control, from health education and early diagnosis to treatment and aftercare. This study provides valuable reference information for both clinicians and health administrators, as well as a baseline for more detailed studies of patient survival for individual anatomical sites.

Mixture models for cancer survival analysis: application to population-based data with covariates.

The interest in estimating the probability of cure has been increasing in cancer survival analysis as the curability of many cancer diseases is becoming a reality. Mixture survival models provide a way of modelling time to death when cure is possible, simultaneously estimating death hazard of fatal cases and the proportion of cured case. In this paper we propose an application of a parametric mixture model to relative survival rates of colon cancer patients from the Finnish population-based cancer registry, and including major survival determinants as explicative covariates. Disentangling survival into two different components greatly facilitates the analysis and the interpretation of the role of prognostic factors on survival patterns. For example, age plays a different role in determining, from one side, the probability of cure, and, from the other side, the life expectancy of fatal cases. The results support the hypothesis that observed survival trends are really due to a real prognostic gain for more recently diagnosed patients.

Implementation of screening as a public health policy: issues in design and evaluation.

OBJECTIVE: To propose principles of design and measures of effect for cancer screening as a public health policy. MATERIAL: Finnish routine screening programme with mammography. DESIGN: Evaluation of mortality from breast cancer by before-after time trends among Finnish women, by geographical (by municipalities) comparisons, and by intention to screen at an individual level with individual controls who were cluster randomised and matched for age. OUTCOME MEASURES: Standardised mortality ratios (SMRs) from breast cancer (total), SMRs from breast cancers diagnosed during the screening programme (refined), deaths prevented, prolongation of life for each breast cancer detected, for each death prevented, for each compliant woman, for each screen, and for each invitation. Relative prolongation of life--that is, time gained versus time spent. RESULTS: SMRs only at an individual level with deaths from cancers diagnosed during the screening programme and individually selected controls showed 24% protection, whereas the other SMR measures were too crude or biased because of dilution and selection. Prolongation of life varied from 15 years for each death prevented to two days for each woman screened, with approximation for the prolongation relative to time spent of 3 to 1. CONCLUSIONS: A public health policy should be introduced gradually. Those not covered immediately by the policy serve as controls and they should be randomly allocated. The most relevant outcome measure is prolongation of life, and for public health purposes it should be given per unit of intervention, such as screen or invitation, and also related to the time spent for the intervention. Such gains are often small in a Western society, which implies that medicine, including research, should focus more on other aspects of life than length.

Fallout from Chernobyl and incidence of childhood leukaemia in Finland, 1976-92.

OBJECTIVE: To assess effects of fallout from Chernobyl on incidence of childhood leukaemia in Finland. DESIGN: Nationwide cohort study. External exposure measured for 455 Finnish municipalities with instruments driven 19,000 km throughout the country. Values specific to municipalities corrected for shielding due to houses and fallout from A bomb testing. Internal exposure estimated from whole body measurements on a random sample of 81 children. Mean effective dose for two years after incident calculated from these measurements. Data on childhood leukaemia obtained from Finnish cancer registry and verified through hospitals treating childhood cancers. SETTING: Finland, one of the countries most heavily contaminated by the Chernobyl accident; the population was divided into fifths by exposure. SUBJECTS: Children aged 0-14 years in 1976-92. MAIN OUTCOME MEASURES: Standardised incidence ratio of childhood leukaemia and relative excess risk of childhood leukaemia per mSv. From incidence data of Finnish cancer registry for 1976-85, expected numbers specific to sex and age group (0-4, 5-9, and 10-14 years) were calculated for each municipality for three periods (1976-85, 1986-8, and 1989-92) and pooled as exposure fifths. Dose response was estimated as regression slope of standardised incidence ratios on mean doses for fifths for each period. RESULTS: Population weighted mean effective doses for first two years after the accident were 410 microSv for the whole country and 970 microSv for the population fifth with the highest dose. In all Finland the incidence of childhood leukaemia did not increase 1976-92. The relative excess risk 1989-92 was not significantly different from zero (7% per mSv; 95% confidence interval -27% to 41%). CONCLUSIONS: An important increase in childhood leukaemia can be excluded. Any effect is smaller than eight extra cases per million children per year in Finland. The results are consistent with the magnitude of effect expected.

PIP: The objective of a nationwide cohort study was to assess the effects of fallout from Chernobyl on the incidence of childhood leukemia in Finland, one of the countries most heavily contaminated by the Chernobyl accident. External exposure was measured with instruments driven by car 19,000 km throughout 455 Finnish municipalities, where the population was divided into fifths by exposure. Values specific to municipalities were corrected for shielding due to houses and fallout from A-bomb testing. Internal exposure estimated from whole body measurements on a random sample of 81 children aged 0-14 years during 1976-1992 and 5-15 in June, 1986, and April, 1988. Mean effective doses from cesium-134 and cesium-137 for 2 years after the incident were calculated from these measurements. Data on childhood leukemia cases that had occurred in children aged 0-14 years during 1975-1992 were obtained from the Finnish cancer registry and verified through each of the 5 university hospitals treating childhood leukemia. Standardized incidence ratio of childhood leukemia and relative excess risk of childhood leukemia per milli sievert (mSv) was measured. From incidence data of the Finnish cancer registry for 1976-1985, expected numbers specific to sex and age group (0-4, 5-9, and 10-14 years) were calculated for each municipality for 3 periods (1976-85, 1986-8, and 1989-92) and pooled as exposure fifths. Dose response was estimated as regression slope of standardized incidence ratios on mean doses for fifths for each period. Population-weighted mean effective doses for first 2 years after the accident were 410 micro Sv for the whole country and 970 micro Sv for the population fifth with the highest dose. In all Finland, the incidence of childhood leukemia did not increase during 1976-1992. The relative excess risk 1989-1992 was not significantly different from zero (7% per mSv; 95% confidence interval -27% to 41%). An important increase in childhood leukemia can be excluded. Any effect is smaller than 8 extra cases per million children per year in Finland.